Snap action electric switch mechanism



Sept. 21, 1965 c. w. KUHN ETAL 3,207,868

SNAP ACTION ELECTRIC SWITCH MECHANISM Original Filed Feb. 28, 1962 5Sheets-Sheet 1 30g 30b g 1 iIllllll Sept. 21, 1965 c. w. KUHN ETAL3,207,868

SNAP ACTION ELECTRIC SWITCH MECHANISM Original Filed Feb. 28, 1962 5Sheets-Sheet 2 62 44 30g 52 30b 58a, 8

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Sept. 21, 1965 c. w. KUHN ETAL 3,207,868

SNAP ACTION ELECTRIC SWITCH MECHANISM Original Filed Feb. 28, 1962 5Sheets-Sheet 3 .9 44 548 y 5tk$fl 6 \llllu lull Sept. 21, 1965 c. w.KUHN ETAL 3,207,868

SNAP ACTION ELECTRIC SWITCH MECHANISM Original Filed Feb. 28, 1962 5Sheets-Sheet 4 36 JR 74f 74a 308 g 1 HH 5 2 2 23 ER 42; sacilfig i%55g33 48am J gmwko-ma [llll F b 42a 42b 42a Q Sept. 21, 1965 c. w. KUHNETAL SNAP ACTI ON ELECTRIC SWITCH MECHANISM 5 Sheets-Sheet 5 OriginalFiled Feb. 28, 1962 United States Patent SNAP ACTION ELECTRIC SWITCHMECHANISM Clarence W. Kuhn, Wanwatosa, and Charles R. Smith, Mequon,Wis., assignors to Cutler-Hammer, line, Milwaukee, Wis., a corporationof Delaware Original application Feb. 28, 1962, Ser. No. 176,354, nowIatent No. 3,135,849, dated June 2, I964. Divided and this applicationNov. 14, 1963, Ser. No. 323,701

9 Claims. (Cl. 20067) This application is a division of our applicationSerial No. 176,354, filed February 28, 1962, now US. Patent No.3,135,849.

This invention relates to improved snap action electric switchmechanism.

While not limited thereto, the mechanism of the present invention iswell suited for use in thermostatic control devices of the kinddisclosed in said Patent No. 3,135,849.

The object of the present invention is to provide an improved snapacting switch mechanism which has two stable operating conditions andprovides fast make and break contact operation when positively drivenfrom one to another of its stable operating conditions.

Other objects and advantages of the invention will hereinafter appear.

The accompanying drawings illustrate preferred embodiments which willnow be described in detail, it being understood that the embodimentsillustrated are susceptible of various modifications without departingfrom the scope of the appended claims.

In the drawings:

FIGURE 1 is a side elevation view of a thermostatic control switchconstructed in accordance with the invention;

FIG. 2 is a right end view of the control switch shown in FIG. 1;

FIG. 3 is a view in cross section taken along the line 33 of FIG. 2;

FIG. 4 is a view like FIG. 3 but showing the control switch in anotheroperating condition;

FIG. 5 is a top plan view with a cover removed to show interiormechanism;

FIG. 6 is a view in cross section taken along the line 66 of FIG. 3;

FIG. 7 is a fragmentary view partially in cross section taken along theline 77 of FIG. 3;

FIG. 8 is a view in cross section taken along the line 88 of FIG. 4;

FIG. 9 is a top plan view of a lever assembly used in the controlswitch;

FIG. 10 is a view showing the parts of the lever assembly of FIG. 9 inexploded relation;

FIG. 11 is a view like FIG. 5 but to smaller scale and with certainmechanism removed;

FIG. 12 is a fragmentary view taken along the line 12-12 of FIG. 3;

FIG. 13 is a top plan view of a part in the switch mechanism;

FIG. 14 shows one operating condition of certain parts used in theswitch mechanism of the control switch; and

FIG. 15 is like FIG. 14 but shows the same parts in another operatingcondition.

Referring particularly to FIGS. 1 to 13, they disclose a preferred andbasic form of refrigerator control embodying the invention whichcomprises a thermal responsive power element 30, an operating mechanismenclosing case 32, and a range adjusting knob 34. This form is aso-called straight range version wherein cut-in and cut-out points aresimultaneously adjustable while maintaining the dilferential betweensuch points substantially constant.

Power element 30 is provided with a cup-shaped portion "ice 30a, a pairof side frame portions 3% which integrally join with portion 30a onopposite sides at the upper end of the latter. At corresponding endsportions 30b are provided with integral tabs 300 (see FIG. 5) whichextend through slots in a mounting bracket 36 and are upset over theopposite side of bracket 36 to secure the latter in place.

As best shown in FIGS. 3 and 4, power element 30 is provided with adiaphragm 3% which is suitably secured in a sealed relation to the innerwall of the cup portion 30a to form an enclosed diaphragm chamber 38therewith. A capillary tube 40 penetrates and is sealed to a bossportion 306 which extends downward at one side of the underside ofportion 30a. Tube 40, as is well known, is of some definite length andits bore and diaphragm chamber 38 of element 30 are provided with asuitable fill of gas such as Freon (F-22 or F-12) or methyl chloride.Diaphragm 36d is preferably formed in accordance with the teaching ofthe Smith Patent No. 2,751,935 so that it will move outwardly andinwardly in a linear relation to changes in pressure of the gas in thechamber 38 and tube 40.

A base 42 formed of a suitable molded electric insulating material seatsat its lower end against the upper edge of cup-portion 39a on oppositesides between the side from portion 39a and at one end against bracket36. Tabs 30f struck out of the portions 30b are bent into recesses 42a(see FIGS. 1 and 5) formed in the outer surfaces of the aforementionedsides of base 42 and serve to secure the latter and power element 30 inassembled relation.

A cover 44 formed of a suitable insulating material seats against theupper surface of base 42 and is secured in place by inwardly extendingtabs Stig formed along the upper edges of the portions 30b.

A stationary contact 46 is mounted on an arm 43a of stationary contactterminal member 48 (see FIGS. 5 and 11) that seats within base 42 whereit is secured by a screw 50. A movable contact 52 is secured inoverlying working relation to contact 46 to the free end of a centralhollow rectangular portion 54a of a metallic reed member 54 which is ofa form best shown in FIG. 13. At its other end member 54 is providedwith spaced apart openings to accommodate screws 56 which also penetratethe arm 58a of a terminal member 58 that overlies and contacts the lastmentioned end of member 54 to secure the latter and terminal member 58in place in base 42.

As shown in FIG. 13, member 54 is provided with legs 54b which arespaced apart and extend parallel with the longitudinal sides of theportions 54a. At their outer ends the portions 54b have integralportions 540 that extend inwardly toward a tab 54d integrally formed onthe free end of portion 54a. Portions 54c have booked lips 54e thatextend generally parallel with the portions 54b.

Reed member 54 is formed to accurate dimensions by suitably blanking thesame from thin flat stock of a spring temper material, such as berylliumcopper alloy. Mounting recesses for member 54 and terminal member 58 areso formed that when the same are initially secured in base 42 by screws56 contact 52 will be forced into engagement with contact 46 with somepre-bending of the portion 54a thereby establishing a minimum normalengagement pressure between contacts 52 and 46.

A C-shaped flipper spring 60 has a slot 60a formed therein (see FIGS. 3,4, 5, 12, 14 and 15) and the tab 54d of member 54 extends therethrough.The portions 540 and 54e of each of the legs 54]) also extend or hookover the web 60b of spring 60 with the portions 54e extending into theslot 66a. The web 6% narrows and terminates at an end 600 that engagesin a V-shaped notch 62a formed in one end of a molded drive lever 62.Flipper spring 60 is formed by blanking from thin flat stock ofstainless steel which has been suitably heat treated and tempered. TheC-shape configuration of spring 60 is imparted in assembling it to thereed member 54 and drive lever 62, but preformed C-shape springs canalso be used.

Drive lever 62 at its opposite end is provided with a V-shaped notch 62bthat engages on the inner edge 54f of the end portion 54g bounding oneend of the central opening 5411 in member 54 to provide a pivot fulcrumpoint for lever 62. As viewed in FIG. 3, notch 62a is below the plane ofmember 54 and the forces developed in spring 60 hold the tab 54d inengagement with a lateral stop finger 58d integrally formed withterminal member 58. In such position of member 54 contact 52 is held outof engagement from contact 46 thereby interrupting circuit.

If drive lever 62 is pivoted counterclockwise about its pivot fulcrum atnotch 62b the end 60c of spring 60 will move upwardly and be compressed,and the upward component of force exerted by spring 60 on the member 54decreases as the angle between its ends and the plane of member 54decreases. A null point is reached where the upward force exerted byspring 60 is equal to the downward force exerted by member 54 due to itsaforementioned bending. Any further counterclockwise movement of lever62 permits tab 54d, and hence portion 54a, to move downwardly to engagecontact 52 with contact 46. Before the end 60c moves across the plane ofthe legs 54b, the force exerted by spring 60 reverses to exert avertical downward component, and a toggle action takes place causingspring 60 to move rapidly with lost motion the width of its slot 60a,minus the thickness of member 54, to engage along the upper margin ofits slot as depicted in FIG. and drive tab 54d downwardly and closecontact 52 upon contact 46. In the closed position of the contacts,shown in FIGS. 4 and 15, the force developed in spring 60 appliedthrough the upper side of slot 60:: against tab 54d is added to theaforementioned prebending stress in member 54 to hold contact 52 againstcontact 46. Overtravel of lever 62 in the clockwise direction is limitedby engagement of one of the projections 620 with a tab 580 whichoverlies such projection.

Assuming that contact 52 is closed against contact 46 as shown in FIG.4, if drive lever 62 is pivoted clockwise about its notch 62b the end60c of spring 60 will move downwardly along an arc and be compressed.This increases the force developed in spring 6%), but because of itschanging angle relative to the plane of reed member 54the downwardvertical component of force exerted on tab 54d is decreased whichreduces the contact engagement pressure. When notch 62a is in line withlegs 54!) the vertical component of force exerted by spring 60 on member54 becomes zero. As lever 62 continues to pivot clockwise, the verticalcomponent of force exerted by spring 60 reverses and a position isreached where the upward force exerted by spring 62 on member 54 isbalanced by the downward forces exerted by legs 54b and a balance offorces exists. Only the aforementioned prebending stress of member 54provides contact engagement pressure. Any additional clockwise movementof lever 62 increases the vertical component exerted by spring 60 andlegs 54:: will move the distance of slot 66a (less the thickness ofmember 54) and spring 60 will toggle member 54 rapidly upwardly to movecontact 52 from engagement with contact 46. Member 54 is limited inupward travel by engagement of the upper surface of its tab 54d withstop finger 58d which is an integral part of member 58. Similarly, theintegral projections 62c on drive lever 62 engage the lower surfaces ofrecesses 42b, formed in base 42 to limit overtravel movement of thelever in the clockwise direction.

Between drive lever 62 and diaphragm d a lever motion multiplying andrange differential adjusting system is interposed. Referringparticularly to FIGS. 3, 4, 8, 9 and 10, the motion multiplying systemincludes a thrust plate 66, a range lever 68, a cut-in lever 70, acut-out lever 72, a stabilizing leaf member 74 and a biasing spring 76.

Thrust plate 66 bears centrally against the diaphragm 30d, anddiametrically opposite legs 66a bear at their arcuate upper ends againstthe outer arms 686 of range lever 68. Lever 68 bears at its one end 6811against the edge of a range adjusting cam 78. At the tip of its oppositeangularly upward end 6811, lever 68 bears against the lower sides of thelevers 70 and 72. Lever 70 pivots against the lower end of an adjustingscrew 80, and lever 72 bears at its corresponding end against the lowerend of an adjusting screw 82.

Bias spring 76 seats at its upper end in a recess 42d formed in base 42,and terminates at its other end in a coaxial straight end that bears ina recess in the upper surface of cut-out lever 72. The spring 76develops a counterclockwise torque on lever 72 about its pivot on theend of screw 82.

As best seen in FIGS. 8, 9 and 10, plate 66 and levers 68, 70 and 72 areheld together in assembled relation by leaf member 74 which ispreferably formed of thin flexible spring stock. Levers 70 and 72 arespot welded to the ends of the outer legs 74a and 741;, respectively,and the plate 66 is spot welded on its upper surface to the end of thecentral leg 740 of member 74 with the legs 66:: of plate 66 straddlingthe outer margin of leg 74c. Range lever 68 is spot welded at its end68b to the intermediate connecting bight 74d of member 74. This assemblyis secured and located in base 42 by means of spaced downwardlyprojecting lugs 42c formed in the base molding which penetrate openings74c formed in leaf member 74. Oppositely disposed tabs 74 formed in themargin of the latter openings grip the sides of lugs 42a and dig in toprevent withdrawal therefrom. Stabilizing member 74 provides lateralstabilizing for plate 66 and levers 68, 70 and 72 and flexes to permitsuch plate and levers to move and pivot as required of the lever. Theamount of flexing required of member 74 in normal operation is minimizedby making the attachments thereto as close as possible to the pivotpoints of the levers.

As best seen in FIGS. 3, 4 and 9, lever 70 has an angularly upturnedportion 70:: which engages on the un der surface of a semi-cylindricalboss 62d formed on drive lever 62. Lever 72 has a generally C-shapedfree end 72a which overlies the boss 62d in a recess 62c formed in lever62 and engages with boss 62d to pivot lever 62 clockwise underdecreasing power element pressure changes as will hereinafter beexplained.

Range adjusting cam 78 is provided with a central opening and is mountedon a cylindrical boss 42g formed on base 42. A spring washer 86frictionally gripping the periphery of an inner concentric boss 42;bears against cam 78 to hold it against axial displacement. A member 88journaled for rotational movement in mounting bracket 36 has a lug 880which interfits with cam 78 in an opening 78a formed in the latter. Onthe outer side of bracket 36 member 88 penetrates and is non-rotatablyupset over a U-shaped member 90 to which range adjusting knob 34 isfitted. The portion 881) has a triangular shaped high point 880 whichwhen knob 34 is turned to its counterclockwise extreme limit (whenlooking in from the left in FIG. 1) engages the end 62 of a hook portion62g of drive lever 62 to pivot the latter to a clockwise extremeposition wherein it manually toggles member 54 to and holds it in aposition disengaging contacts 52 and 46. The last mentioned extremelimit is determined when member 90 engages a raised projection 36astruck up from the bracket 36.

In one preferred embodiment of cam 78 its peripheral form will be likethat depicted in FIG. 7. As viewed in FIG. 7, if cam is rotatedclockwise the radial distance be tween its point of engagement with theend 68b of range lever 68 and its axis of rotation decreases therebycausing the end 6812 to move upwardly as member 68 pivots on the ends oflegs 66a of thrust plate. Consequently lever 68 pivots clockwise asviewed in FIGS. 3 and 4,

thereby lowering its end 68d which in turn causes cut-in and cut-outlevers 7i and '72 to pivot counterclockwise about the ends of thedifferential adjusting screws 80 and 83. As will hereinafter be apparentthe higher the position of the end 68b of range lever 68 as establishedby cam 78, the higher will be the pressures in power element 39 at whichcontact 52 will be engaged and subsequently disengaged from contact 46.

Let it be assumed that the contacts 52 and 46 are initially open asdepicted in FIG. 3, and that cam 78 is given an intermediate adjustmentdepicted. Now if element 40 is subjected to an increasing temperature,the pressure in chamber 38 will increase and diaphragm 30d will moveupwardly. Thrust plate 66 moves upwardly with diaphragm 3%. which inturn pivots range lever 68 counterclockwise at its point of engagementwith the edge of cam 78. Such movement of lever 68 causes both thecut-in and cut-out levers 7th and 72 to be pivoted clockwise about theirpivot points on the ends of diflerential adjusting screws 8%) and 82. Ascut-in lever 70 continues to pivot clockwise it ultimately engages thelower side of boss 62d of drive lever 62. Further clockwise pivoting oflever 70 results in counterclockwise pivoting of lever 62 to provide theclosing of contact 52 to contact 4-6 as hereinbefore described. Thus theaforedescribed levers 63, 70, 72 and 62 attain the positions depicted inFIG. 4.

Now assume, as a result of closure of contacts 52 and 46 and operationof refrigerating apparatus controlled by such contacts, that thetemperature to which temperature responsive element 4% is subjecteddecreases. This causes a reduction in vapor or gas pressure in chamber38 and diaphragm 30d moves downwardly. Bias spring 76 acting on cut-outlever 72 causes the latter and range lever 68 to pivot counterclockwiseand clockwise respectively in following the downward movement ofdiaphragm 30d. Ultimately the C-shaped end 72a of cut-out lever 72engages the boss 62d on its upper side and pivots drive lever 62clockwise. When lever 62 is pivoted clockwise sufliciently contacts 52and 46 are toggled opened as hereinbefore described. As will beunderstood the force exerted by spring 76 must be sufiicient to efiectoperation of the snap action switch mechanism but should not have aspring rate greater than necessary to minimize the loading on diaphragm30d. Spring rates in the range of 2 to 3 lbs. per inch have proved to besatisfactory for spring 76.

It will be apparent that the levers 68 and 70 or 72 provide considerablemotion amplification for any upward or downward movement of diaphragm30d. For a given setting of range adjusting cam 73, diaphragm 30d,thrust plate 66 and levers 68, 70 and 72 take new positions for eachunit change in pressure developed in element 40.

The spacing between the ends 70a and 72a which underlie and overlie theboss 62d of drive lever 62 determines the diflerential betweetn cut-inand cut-out toggle operation to close and open the contacts 52 and 46.This differential is adjustable in accordance with the adjustment of thescrews 8% and 82. Cut-in and cut-out differential adjustments areinitially established by subjecting element 4t) to a low cut-outtemperature, say 20 F. for a given intermediate adjustment of cam 78.When element 40 is stabilized at 20 adjusting screw 82 is adjusted topivot lever 72 counterclockwise and engage boss 62d of drive lever 62and is continued until toggle action of the contact operating mechanismoccurs and opens contacts 52 and 46. If it is desired that contacts 52and 46 reclose at a 10 higher temperature, then element 40 will next besubjected and stabilized at such a temperature, e.g., 30 F. andadjusting screw 80 is turned to pivot lever 70 clockwise on end 68d oflever 68 to engage boss 62d and pivot drive lever 62 until the point isreached where the contact operating mechanism is toggled to closecontacts 52 and 46. Thereafter for any given positioning of cam 78 thecut-in and cut-out temperatures will al ways have the same fixeddifferential.

We claim:

1. In a snap action switch mechanism, a thin flexible member having afixed end portion and three, parallel spaced apart portions which areintegral with and depend from said end portion, the center one of saidthree portions having a central opening formed therein, an operatinglever pivoted on an inner edge of said center portion adjacent said endportion, and a snap member formed of thin spring metal having atransverse slot adjacent one end through which said center portionextends and be ing longitudinally bowed with its other end seatingagainst said lever, said slot being substantially wider along thelongitudinal dimension of said snap member than the thickness of saidflexible member, said other two portions of said flexible memberanchoring the first mentioned end of said spring against longitudinaland transverse movement on said center portion, and said lever beingpivotally movable in opposite directions to move said other end of saidsnap member across the plane of said center portion of said flexiblemember to provide lost motion, snap toggling of said center portion bysaid snap member from one stable position to another and vice versa.

2. The combination according to claim 1 wherein said lever is providedwith V-shaped bearing notches where it engages with said flexible memberand said snap member.

3. The combination according to claim 1 wherein said other two portionsof said flexible member adjacent their ends are turned in toward eachother and through said slot in said snap member toward said end portionof said flexible member.

4. In a snap action switch, a molded insulating base, an electricalterminal member having a stationary contact tip mounted on said base, athin flexible electrical conducting member having an end portion securedto said base and having three, spaced apart parallel portions integralwith and depending from said end portion, the center of said threeportions having a contact tip mounted thereon in line with that of saidterminal member and having a central opening formed therein, a drivelever of insulating material pivoted on an inside edge of said centerportion adjacent said end portion, and a snap member formed of thinspring metal and having a transverseslot formed adjacent one end throughwhich said center portion extends and being longitudinally bowed withits other end seating on said lever, said slot being substantially wideralong the longitudinal dimension of said snap member than the thicknessof said flexible member, said other two portions of said flexible memberanchoring the first mentioned end of said spring against longitudinaland transverse movement on said center portion and said drive lever whendriven in opposite directions pivoting said other end of said snapmembers across the plane of said flexible member to provide lost motionsnap toggling of said center portion by said snap member from one stableposition to another.

5. The combination according to claim 4 wherein said flexible member isprestressed to engage its contact tip with the other contact tip andwherein such contact tip engagement is maintained until said snap memberis toggled in one direction to take up the lost motion afforded by thewidth of said slot and positively move said flexible member in contactdisengaging direction.

6. The combination according to claim 4 wherein a second electricalterminal member is secured to said base in overlying engaging relationto said end portion of said flexible member and is provided with aportion overlying said center portion of said flexible member to providea limit stop for said center portion when the latter moves to disengageits contact tip from the other contact tip.

'7. The combination according to claim 6 wherein said base and saidsecond electrical conducting member having abutments which are engagedby a portion of said lever to limit the pivotal movement of the latterin each of its reverse directions.

8. The combination according to claim 4 wherein said other two portionsof said flexible member are relatively narrow and adjacent their endsare turned toward each other and through the slot in said snap membertoward said end portion of said flexible member to longitudinally andtransversely anchor the first mentioned end of said snap member on saidcenter portion.

9. The combination according to claim 4 wherein said drive lever isprovided with V-shaped bearing notches O (I? wherein it engages withsaid flexible and snap members.

References Cited by the Examiner UNITED STATES PATENTS 2,197,229 4/40\Vaddell 20067 X 2,460,087 1/49 Hollis 20067 2,813,946 11/57 Cox 20067 X2,905,782 9/59 Chapin et a1. 200-67 2,927,171 3/60 Rhodes 20067 BERNARDA. GILHEANY, Primary Examiner.

1. IN A SNAP ACTION SWITCH MECHANISM, A THIN FLEXIBLE MEMBER HAVING AFIXED END PORTION AND THREE, PARALLE SPACED APART PORTIONS WHICH AREINTEGRAL WITH AND DEPEND FROM SAID END PORTION, THE CENTER ONE OF SAIDTHREE PORTIONS HAVING A CENTRAL OPENING FORMED THEREIN, AN OPERATINGLEVER PIVOTED ON AN INNER EDGE OF SAID CENTER PORTION ADJACENT SAID ENDPORTION, AND A SNAP MEMBER FORMED OF THIN SPRING METAL HAVING ATRANSVERSE SLOT ADJACENT ONE END THROUGH WHICH SAID CENTER PORTIONEXTENDS AND BEING LONGITUDINALLY BOWED WITH ITS OTHER END SEATINGAGAINST SAID LEVER, SAID SLOT BEING SUBSTANTIALLY WIDER ALONG THELONGITUDINAL DIMENSION OF SAID SNAP MEMBER THAN THE THICKNESS OF SAIDFLEXIBLE MEMBER, SAID OTHER TWO PORTIONS OF SAID FLEXIBLE MEMBERANCHORING THE FIRST MENTIONED END OF SAID SPRING AGAINST LONGITUDINALAND TRANSVERSE MOVEMENT ON SAID CENTER PORTION, AND SAID LEVER BEINGPIVOTALLY MOVABLE IN OPPOSITE DIRECTIONS TO MOVE SAID OTHER END OF SAIDSNAP MEMBER ACROSS THE PLANE OF SAID CENTER PORTION OF SAID FLEXIBLEMEMBER TO PROVIDE LOST MOTION, SNAP TOGGLING OF SAID CENTER PORTION BYSAID SNAP MEMBER FROM ONE STABLE POSITION TO ANOTHER AND VICE VERSA.